drm/bridge: dw-hdmi: Plug atomic state hooks to the default implementation

Add atomic_duplicate_state/atomic_destroy_state/atomic_reset bridge
funcs to allow setup of atomic bridge state.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jernej Škrabec <jernej.skrabec@siol.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20200304104052.17196-4-narmstrong@baylibre.com